Museum specimens provide resource for comparisons over time, but many traits cannot be measured from specimens
What if researchers could have access live animals from a historical time point that had frozen in time?
For some species, seeds, eggs, cysts, spores can be preserved in soil or ice and revived years or even centuries later
Question: Can Daphnia evolve to cope with global warming?
Approach 1: Experimental evolution
Approach 2: Resurrection ecology
CTmax - upper threshold of temperature that an organism can function normally
Approach 1: Experimental evolution - Evolved Daphnia under control and warmed conditions for 2 years
Approach 2: Resurrection ecology - Hatched Daphnia from historic and contemporary sediment layers
Conclusion: Thermal tolerance in Daphnia can evolve over short time scales in response to global warming
Daphnia not only interact strongly with its phytoplankton food resource, but also with other components of marine food webs
Some organisms can adapt rapidly, but not always rapidly enough
What happens when the rate of environmental change exceeds the ability of populations to adapt?
Some organisms can adapt rapidly, but not always rapidly enough
For example, some populations do not have enough genetic variation to track forecast changes in climate
A 2°C rise in the next 60 years (12 birch generations) is predicted to advance budburst by 40 days
Billington & Pelham (1991) predicted how much change would need to occur per generation versus current population variation
Predicted change would be impossible
Why can some species evolve quickly enough to cope with global warming while others can’t?
What traits make a species more likely to exhibit the adapt response?
BRAINSTORM: All else being equal, we expect higher likelihood of adaptation in organisms with…
Higher trait heritability (for the relevant traits)
Adaptation cannot occur if a trait is not inherited
Heritability varies by trait
More existing genetic variation (in relevant traits)
Adaptation from existing or “standing” genetic variation can be fast because the population does not have to “wait” for new mutations to occur.
More existing genetic variation (in relevant traits)
Contrast that with waiting for a new mutation
Higher mutation rates
Faster mutation rates generate more variation on which selection can act
Faster generation times
The relative velocity of environmental change is slower for organisms that can go through many generations each year
Larger population sizes
Larger populations are more likely to have standing variation and are less likely to be decimated by chance events
Other factors like amount of gene flow and how traits are linked to each other in the genome also matter
The survival of tuskless females across this 28-year period was estimated to five times that of tusked individuals in Gorongosa National Park (Campbell-Station et al. 2021)
